Usually, employment at the UN means participation in volunteer missions around the world. However, provided that you already have work experience in international organizations, you can apply for a permanent position.
Even if you have a suitable specialty and qualification level to work in the UN, it will be difficult to get a job in one of its organizations. This is primarily due to the fact that the quota allocated to citizens of Russia and many CIS countries is exceeded every year. Go to the Russian-language UN website (http://www.un.org/ru/) and check the size of the quota for the next year in order to really assess your opportunities for getting a job.
Go to http://www.unsystem.org for a list of UN organizations websites. Visit those of them, work in which you would be interested. Find out the conditions for applying for the vacancies offered by each of these divisions.
To apply for employment, first go to http://careers.un.org and register as an applicant for your chosen position.
It may also happen that you can start working at the UN, literally without leaving your home, since you live in a region where its official representatives do not yet exist, or where help from this organization is required. In this case, control over your work will be carried out by local authorities, with which you will have to coordinate all your further actions.
Depending on which region of the country and the world of the UN requires employees of your qualifications, you will have to constantly coordinate your actions with institutions and departments of various levels (up to ministries).
Even if you decide to join the ranks of volunteers in one of the missions in not the most prosperous regions, your activities can be different: from saving a population dying from exotic diseases to working as a temporary consultant on international issues.
Before getting a referral to work in the UN structure, take a test and pass exams in the official language of the country of your choice. The testing program usually includes questions regarding international law and the legislation of the state in which you are applying for a job.